The present invention relates generally to electromagnetic circuit breakers. More particularly, the present invention relates to a circuit breaker having an encapsulated auxiliary electromagnetic coil fitted onto a primary bobbin adjacent a pole piece, and to an insulated bobbin and bobbin housing which encapsulates an auxiliary electromagnetic coil.
Electromagnetic circuit breakers provide a load current/voltage through a primary electromagnetic coil that encompasses a delay tube in which a plunger is adapted to be drawn towards a pole piece at the end of the delay tube by reason of the magnetic flux created in a frame and armature. Once the plunger is drawn to the pole piece because of impermissible conditions, the circuit breaker is tripped causing an open circuit.
Secondary methods of tripping electromagnetic circuit breakers are frequently desirable. A second electromagnetic coil, referred to herein as an auxiliary electromagnetic coil or an auxiliary coil, may be added to the circuitry of the circuit breaker facilitating the tripping of the circuit breaker in response to an over current/voltage condition on the second coil. Typically, the auxiliary coil, and the circuitry connected thereto, must be separated from the primary coil to prevent arcing resulting in a short circuit and premature tripping of the circuit breaker. The UL Laboratories, in UL 489 , specifies a minimum spacing between two conductors within a circuit breaker effectively preventing the utilization of conventional, uninsulated auxiliary and primary coils within the same circuit breaker assembly.
U.S. Pat. No. 4,982,174 (""174), issued to Fasano on Jan. 1, 1991 and assigned to the common assignee, Carlingswitch, Inc., is incorporated herein by reference in its entirety. The patent ""174 discloses a molded split case electromagnetic circuit breaker assembly having a second coil, configured as a shunt coil, fitted on a bobbin that is selectively mounted on the bobbin containing the primary electromagnetic coil for the breaker. The circuit breaker housing is adapted to receive either a molded switch subassembly or a terminal strip that is held in place by the primary terminals of the breaker and is adapted to support auxiliary terminals that operate the shunt coil. The magnetic wire of the shunt coil of ""174 is exposed to the interior of the circuit breaker housing so that an arc or an induced magnetic field may occur thereby prematurely tripping the circuit breaker.
An auxiliary coil must be magnetically separated from the primary coil to avoid an induced magnetic field in the auxiliary coil. Either an induced magnetic field or a flow of current in the auxiliary coil will result in premature tripping of the circuit breaker.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed.
The present invention is a circuit breaker having an encapsulated auxiliary electromagnetic coil fitted onto the primary bobbin adjacent the pole piece, and a dielectric auxiliary bobbin and bobbin housing which encapsulate the auxiliary coil. Three circuit breaker configurations utilizing the insulated auxiliary bobbin and bobbin housing are contemplated in the present invention. The dielectric bobbin housing and the auxiliary bobbin are both composed of a dielectric polymeric material, preferably a liquid-crystal polymer, having substantial insulator properties.
The first configuration utilizes an encapsulated auxiliary electromagnetic coil in a split case circuit breaker without a primary coil. The auxiliary coil is connected to the load through either the conventional load terminal or a separate auxiliary load terminal. The first configuration is utilized as a separate relay contact for a stack of circuit breakers. Actuators are connected through the stack so that if one circuit breaker is tripped, all of the circuit breakers in the stack are tripped. Conventionally, the actuator handles are connected to one another by handle ties. This configuration permits the auxiliary electromagnetic coil to serve as a separate unprotected pole of a multi-pole circuit breaker assembly, thereby facilitating remote tripping of the multi-pole circuit breaker assembly.
The second and third configurations utilize an encapsulated auxiliary electromagnetic coil with split case circuit breaker which has a primary electromagnetic coil arrangement. In the second configuration, the auxiliary coil has a separate circuit having an auxiliary load terminal and an auxiliary line terminal thus forming a four terminal relay configuration. In the third embodiment, the auxiliary coil is connected to the circuit on the load side of the primary coil with a line to a separate auxiliary load terminal forming a three terminal shunt configuration.
An object of the present invention is to provide a second coil for tripping a circuit breaker, which will not cause the circuit breaker to trip unnecessarily, meets the current UL standards, and is fitted on top of the primary coil. The liquid-crystal polymer, with which the bobbin housing and auxiliary bobbin are preferably composed, provides enough insulation to permit the primary and auxiliary coils to be placed in close proximity to one another without requiring the wire of the auxiliary coil to be inconveniently thin.
A further object of the present invention is to provide a second trip coil, the auxiliary coil, which can facilitate additional configurations of a circuit breaker. The auxiliary coil assembly of the current invention permits both shunt and relay circuit configurations within the same circuit breaker. Alternatively, the auxiliary coil may be used alone without a primary coil to form a separate relay for a multi-pole circuit breaker assembly.
Another object of the invention is to provide a trip coil which will trip when a small amount of current, or low voltage, is applied to the coil. A sensitive trip coil results, which can be used in a circuit breaker alone or in conjunction with a primary coil, permitting the remote tripping of the circuit breaker.
These and other objects of the present invention will become readily apparent upon further review of the following specification and claims.